Calgary Mayor Jyoti Gondek said that later today, another pump at the Bearspaw Water Treatment Plant will be turned on, and the next 72 hours may determine if, by the end of this week, water restrictions will be further eased.
"The plan is to turn one more pump on midday today to increase the speed at which water can flow. The water operations team will be using acoustic monitoring and they'll be carefully watching pressure increases over the next 72 hours," she said. "If there are no issues, it is possible that more information about moving to stage two [water restrictions] will be available on Thursday. I cannot stress enough that the next 72 hours are critical to understand how the pipe is responding to the speed of flow. Turning on an additional pump means the pressure has to be carefully monitored, ensuring that we can identify any issues that may exist."
Michael Thompson, General Manager, Infrastructure Services for The City of Calgary explained that monitoring of the pipe over the past few weeks has enabled crews to learn more about the condition of the pipe.
"We have been measuring the pressure at various points along the pipe and using acoustic monitoring devices; we have been listening for snaps in the wires that coil around 350 times each 16-foot-long segment of pipe," Thompson said. "We're particularly focused on wire snaps in the area stretching from where the initial rupture happened to where the repair work was completed. We're not concerned about the sections that were just repaired, but we are watching other sections of the pipe in this stretch."
Last week, three wire snaps were detected in the wires coiling around different segments of the feeder main pipe. He underlined that the wire snaps do not mean that repair or replacement in an emergency manner is needed.
"... But it does mean that we need to be measured and thoughtful in how we proceed. We know people are eager to have outdoor watering restrictions lifted. The key to doing this is increasing the flow of water through the feeder main' the pipe is full of water right now, but it is not moving as quickly as it usually does. By using pumps to increase the speed of the water flow, we will increase the amount of water we can supply to you each day."
He added that Stage Three Water Restrictions remain because the flow of the water through the pipe is only at 55 per cent of normal at this flow rate.
"We need stage three restrictions in place to make sure that water demand doesn't exceed what we can supply. We need 70 per cent flow to be able to move to stage one and stage two restrictions, and then a 75 per cent flow to be able to ease all outdoor watering restrictions."
Thompson said that if no other complications arise, by next Monday there is a possibility that Stage One Water Restrictions may be phased in.
"If we get to stage one restriction, and the pipe is operating as expected, we will once again increase the flow through the pipe, which will allow us to remove all restrictions. We're managing the risk between increased water flow, which will help lessen water restrictions, and the pipe's overall stability," he added. "One of the risks, as we proceed, is that we could detect signs of trouble, like additional wire snaps. That may mean we have to stop increasing the flow through the pipe, this could result in a situation where we have to stay in some form of outdoor water restrictions."
He said that there is also a risk of an additional failure in the pipe.
"Given what we have heard, what we've just all been through, this may be a little alarming to hear. This is part of our calculated risk decision after analysis. We think that the risk is low enough to move ahead with increasing the water flow if a new break were to happen, we're ready to respond."
Thompson also said that later this month the data analysis from the pipe driver device will be available. The deuce was inserted into the pipe to inspect the entire concrete pipe.
"We are waiting for the results from that inspection, and hope to have them by the end of July... We know that there are additional areas of weakness within the pipe, and it will need a medium to long-term rehabilitation plan. We've started to develop options for what that might look like, and we will incorporate the additional information we're going to receive from the pipe diver at the end of July into that rehabilitation plan."
Thompson said some options include placing a liner inside the existing pipe, replacing additional segments of pipe which have lower structural capacity due to wire snaps, reinforcing exterior segments of the pipe, or perhaps installing a new pipe altogether.